The present invention relates generally to analytical devices and methods for monitoring and optionally controlling natural or industrial processes or systems. More specifically, the present invention relates to a fluorometer capable of detecting fluorescent signals emitted by one or more fluorophores present in samples from natural or industrial processes or systems. By using this fluorometer it is possible to monitor and optionally control the process or system.
A fluorometer is an analytical device that typically contains a light source, a means of selecting the desired excitation wavelength range, a sample cell, a means of selecting the desired emission wavelength range and a detector.
A spectrofluorometer is a specific type of fluorometer where the means for selecting the excitation and/or emission wavelength range is performed by a grating. A grating acts to disperse a continuum of light into its components. Spectrofluorometers may be further subdivided into scanning spectrofluorometers, which are those that use a mechanical means to scan the wavelength spectrum based on the position of the grating relative to the excitation source and/or emission (this describes a standard laboratory model fluorometer), or fixed spectrofluorometers where the grating is fixed with respect the emission. The emission (fluorescence) is then directed to an array of detectors. The array of detectors could be charge coupled devices, usually abbreviated xe2x80x9cCCDxe2x80x9d or the array of detectors could be photodiodes. The detectors are then calibrated in the appropriate wavelength units. A commercial device such as this is available from Drysdale and Associates, Inc., P.O. Box 44055, Cincinnati, Ohio 45244 (513) 831-9625. This type of fixed spectrofluorometer still requires the appropriate excitation wavelength selection device, which could be a scanning, grating or filter.
The fluorometers that are most suitable for use under field conditions are not grating spectrofluorometers, rather, they are filter-based fluorometers. A filter-based fluorometer uses a filter to exclude all but the selected wavelength range. In general, currently available and known filter-based fluorometers have one channel with this channel containing an optically appropriate cell.
A light source and an optional excitation filter, are positioned on one side of the optically appropriate cell, and an emission detector and an emission filter are positioned on the opposite side of the optically appropriate cell. A reference detector may optionally be present. Because fluorescence is isotropic, most fluorometers detect any fluorescent light emitted from the fluorophore at a 90xc2x0 angle from the light source in order to minimize collection of any spurious excitation light.
The excitation filter permits light of the chosen excitation wavelength range to pass through the filter and into the cell. When conducting off-line batch testing, a sample of, for example, water from a natural or an industrial water system is placed and held in the optically appropriate cell. When conducting on-line testing the sample of water can flow through the optically appropriate cell. The light is absorbed by a fluorophore present in the water sample, which, in turn, emits a fluorescent light (hereinafter known as a fluorescent signal) having the same or a longer wavelength than the excitation light. The emission filter, which is positioned between the emission detector and the optically appropriate cell, is chosen so as to permit only the light emitted by the fluorophore (the fluorescent signal of the fluorophore) to pass through the filter to the emission detector.
One of the known uses of fluorophores in industrial water systems or in hydrology in general is the use of inert fluorescent tracers for determining the hydraulic losses in an industrial water system. Furthermore, using fluorescent tracers for controlling additive or product dosage to a recirculating or once-through cooling water system is also known (see U.S. Pat. No. 4,783,314). In this method, a fluorescent tracer is combined with one or more additives in a known proportion of tracer to additive(s) and then the mixture is added to the water of a cooling system. A fluorometer is then used to detect the presence and concentration of the fluorescent tracer in the cooling water and therefore the presence and concentration of the amount of additive. A limitation of currently available fluorometers is that, in general, they have only one channel that contains an optical cell for measuring fluorescence in a single process sample (i.e., a one-channel-sample fluorometer). Another limitation of currently available fluorometers is that the majority of known fluorometers are not suitable for measuring fluorescent signal(s) in opaque mediums, such as opaque slurries, opaque colloids and certain opaque Metal Working Fluids.
There exists a need for an fluorometer which is capable of monitoring several process samples using a single apparatus without having to replace a process sample, and the need for fluorometers capable of measuring fluorescent signals in an opaque medium.
The first aspect of the instant claimed invention is a fluorometer comprising:
an excitation light source for generating a collimated beam of excitation light;
a rotatable mirror positioned such that it is capable of accepting a collimated beam of light from said excitation light source and projecting a converging cone of excitation light onto one or more samples;
a sample holder comprising one or more channels, wherein each channel is capable of holding an optical cell containing a sample; and
a detector capable of detecting the fluorescent signals from fluorophores presents in said one or more samples.
The second aspect of the instant claimed invention is a fluorometer comprising:
an excitation light source for generating a collimated beam of excitation light;
a rotatable mirror positioned such that it is capable of accepting a collimated beam of light from said excitation light source and projecting a converging cone of excitation light onto one or more samples;
a sample holder comprising one or more channels, wherein each channel is capable of accepting an optical cell containing a sample;
a detector capable of detecting the fluorescent signals from fluorophores presents in said one or more samples; and
a controller that uses the fluorescent signals detected by said fluorometer for monitoring and/or control of the natural or industrial process from which the samples are taken.
The third aspect of the instant claimed invention is a method of fluorometrically detecting fluorophores present in one or more samples, the method comprising the steps of:
a) providing a fluorometer, wherein said fluorometer is described in the first aspect or in the second aspect of the instant claimed invention;
b) providing one or more samples from a natural or industrial process stream; and
c) using said fluorometer to detect the fluorescent signals of said fluorophores in said samples.